JP7185576B2 - Control device - Google Patents

Description

The present invention relates to control devices.

Conventionally, in electron microscopes, techniques have been proposed for suppressing sample drift caused by operation of a sample stage drive motor or changes in room temperature.
For example, in the scanning electron microscope described in Patent Document 1, the same current is supplied to the motor when the sample is moving and when it is stopped, and the difference in the supplied current is 20% or less to reduce the change in the amount of heat in the motor. and the temperature of the sample stage is controlled to reduce sample drift during observation.

WO2011/145290

For example, in a high-resolution electron microscope, as an actuator for moving a table on which a sample is placed, it is conceivable to use an AC servomotor that moves smoothly even during low-speed driving. When controlling a motor used in an apparatus that requires high-precision positioning drive, such as an electron microscope using an AC servomotor, it is necessary to suppress positional deviation of the sample due to temperature changes caused by heat generated in the motor. is desired.
SUMMARY OF THE INVENTION It is an object of the present invention to provide a control device that can accurately position an object that is moved by driving a motor.

The present invention will be described below. In the following description, the reference numerals and the like of the constituent elements in the embodiments are added in parentheses to facilitate understanding of the present invention, but the present invention is limited to the contents described in the embodiments. is not.
The present invention completed for the above purpose is a control device (100) for a three-phase motor (110) driven to move an object, wherein the target current supplied to the motor (110) is: A target current setting means (120) for setting a d-axis target current (Idt) and a q-axis target current (Iqt) in a dq coordinate system, wherein the target current setting means (120) sets the q-axis target current A control device (100) for increasing the d-axis target current (Idt) when (Iqt) is decreased.

Here, the target current setting means (120) sets the d-axis target current (Idt) to a predetermined current (Idt0 ).
Further, the target current setting means (120) gradually increases the q-axis target current (Iqt) to the predetermined current (Idt0) after a lapse of a predetermined increase time (Ti) from when the q-axis target current (Iqt) is set to zero. The d-axis target current (Idt) may be increased.
Further, the target current setting means (120) sets the q-axis target current (Iqt) to zero when the position command speed (Vpt) is zero and the position deviation (pt-θd) is zero, and the d The shaft target current (Idt) may be increased from zero.

Viewed from another point of view, the present invention is a control device (100) for a three-phase motor (110) driven to move an object, wherein the target current supplied to the motor (110) is d It has target current setting means (120) for setting the d-axis target current (Idt) and the q-axis target current (Iqt) of the -q coordinate system, and the target current setting means (120) includes the q-axis target current ( A control device (100) for decreasing the d-axis target current (Idt) when increasing the Iqt).

Here, the target current setting means (120) may decrease the d-axis target current (Idt) to zero when the q-axis target current (Iqt) is changed from zero to a non-zero value.
Further, the target current setting means (120) gradually reduces the q-axis target current (Iqt) so that it becomes zero after a predetermined decrease time (Td) has elapsed from when the q-axis target current (Iqt) is set to a non-zero value. The axis target current (Idt) may be decreased.
Further, the target current setting means (120) sets the q-axis target current (Iqt) to a non-zero value when the position command speed (Vpt) or the positional deviation (pt-θd) becomes non-zero. , the d-axis target current (Idt) may be decreased.

ADVANTAGE OF THE INVENTION According to this invention, the positioning of the target object moved by the drive of a motor can be performed with high precision.

1 is a diagram showing a schematic configuration of a scanning electron microscope according to an embodiment; FIG. 3 is a diagram showing a schematic configuration of a sample moving stage of the scanning electron microscope according to the present embodiment; FIG. It is the figure seen in the III direction of FIG. 1 is a schematic configuration diagram of a control device; FIG. 1 is a schematic configuration diagram of a control device; FIG. FIG. 5 is a diagram illustrating temporal changes in a d-axis target current set by a d-axis target current setting unit; 9 is a flow chart showing processing for setting a d-axis target current performed by a d-axis target current adjustment unit;

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings.
FIG. 1 is a diagram showing a schematic configuration of a scanning electron microscope according to this embodiment.
FIG. 2 is a diagram showing a schematic configuration of the sample moving stage of the scanning electron microscope according to this embodiment.
FIG. 3 is a view of FIG. 2 viewed in direction III.
Scanning electron microscope 50 according to the present embodiment (hereinafter, sometimes simply referred to as “microscope 50”) is different from the scanning electron microscope described in Patent Document 1 in that x table 33 is moved x The motor 41, the y-motor 61 that moves the y-table 43, and the control device 100 that controls the driving of these motors are different. Differences from the scanning electron microscope described in Patent Document 1 are mainly described below.

A microscope 50 includes an electron gun 1, a condenser lens 2, an objective lens 3, a sample chamber 4, a sample moving stage 5, a secondary electron detector 7, vacuum pumps 9 to 13, and a stage case 14. have. The microscope 50 irradiates the electron beam generated by the electron gun 1 onto the sample S mounted on the sample moving stage 5 in the sample chamber 4 through the condenser lens 2 and the objective lens 3. The incoming secondary electrons are caught by the secondary electron detector 7, and the shape of the surface of the sample S can be observed.

Also, the microscope 50 has a z-table 15 and a tilt table 20 . A mechanism for driving the z-table 15 and a mechanism for driving the tilt table 20 are basically the same as those of the scanning electron microscope described in Patent Document 1, so detailed description thereof will be omitted. .

The microscope 50 has an x-table 33 that moves the sample S in the x-direction. The x-table 33 is attached to the tilt table 20 via cross roller guides 34 . The microscope 50 also has an x ball screw 35 and an x ball screw nut 36 that move the x table 33 . The microscope 50 also has bearings 37 and 38 supporting both ends of the x-ball screw 35, respectively, and bearing housings 39 and 40 supporting the bearings 37 and 38 on the tilt table 20, respectively. The x ball screw nut 36 is fixed to the x table 33 via the x joint 42 .

The microscope 50 also has an x-motor 41 connected to the x-ball screw 35 , an x-coupling 44 , and an x-bracket 45 supporting the x-motor 41 . The x bracket 45 is fixed to the tilt table 20 . The x-table 33 moves in the x-direction by driving the x-motor 41, rotating the x-ball screw 35, and transferring the x-ball screw nut 36, thereby moving the sample S in the x-direction.

The microscope 50 also has a y-table 43 for moving the sample S in the y-direction. The y table 43 is attached to the x table 33 via cross roller guides 54a and 54b. The microscope 50 also has a y ball screw 55 and a y ball screw nut 56 that move the y table 43 . The microscope 50 also has bearings 57 and 58 that support both ends of the y ball screw 55, respectively, and bearing housings 59 and 60 that support the bearings 57 and 58 on the x table 33, respectively. The y ball screw nut 56 is fixed to the y table 43 via the y joint 48 .

The microscope 50 also has a y-motor 61 connected to the y-ball screw 55 , a y-coupling 62 , and a y-bracket 63 supporting the y-motor 61 . The y bracket 63 is fixed to the x table 33 . The y-table 43 moves in the y-direction by driving the y-motor 61, rotating the y-ball screw 55, and transferring the y-ball screw nut 56, thereby moving the sample S in the y-direction.

The microscope 50 also has a rotation table 66 for rotating the sample S. The rotation table 66 is rotatably supported with respect to the y table 43 via bearings (not shown). The microscope 50 also has a worm wheel 67 a and a worm gear 67 b that rotate the rotation table 66 . A worm wheel 67 a is attached to the rotation table 66 . The microscope 50 also has bearings 69 and 70 that support both ends of the worm gear 67b, respectively, and bearing housings 71 and 72 that support the bearings 69 and 70 on the y-table 43, respectively.

The microscope 50 also has an r-motor 73, an r-coupling 74, and an r-bracket 75 that supports the r-motor 73, which are connected to the worm gear 67b. The r bracket 75 is fixed to the y table 43 . The rotation table 66 is rotated by driving the r-motor 73 to rotate the worm gear 67b and the worm wheel 67a, thereby causing the sample S to rotate.

The sample S is adhered to a sample holder 77 , and the sample holder 77 is inserted into and fixed to a holder base 78 attached to the rotation table 66 .
As described above, the sample S is moved in the x, y and z directions, rotated and tilted.

(Regarding motor control)
The x-motor 41, y-motor 61 and r-motor 73 described above can be exemplified as three-phase AC servomotors.
The microscope 50 has a control device 100 that controls driving of the x motor 41 , y motor 61 and r motor 73 . Since the control device 100 controls the x motor 41, the y motor 61, and the r motor 73 in the same manner, the x motor 41, the y motor 61, and the r motor 73 are hereinafter referred to as "motor 110". A manner of controlling 110 will be described.

4 and 5 are schematic configuration diagrams of the control device 100. FIG.
The control device 100 is an arithmetic logic operation circuit including a CPU, ROM, RAM, EEPROM (Electrically Erasable & Programmable Read Only Memory), and the like.
The control device 100 includes a target current setting unit 120 that sets a target current to be supplied to the motor 110, and a control unit 130 that performs feedback control based on the target current set by the target current setting unit 120. there is The functional configuration of the target current setting section 120 is shown in FIG. 4, and the functional configuration of the control section 130 is shown in FIG.

As shown in FIG. 4, the target current setting unit 120 includes a q-axis target current setting unit 121 for setting a q-axis target current Iqt in the dq coordinate system and a d-axis target current setting unit 121 for setting a d-axis target current Idt. and a portion 122 . The dq coordinate system is a rotating orthogonal coordinate system consisting of the d-axis and the q-axis that rotate in synchronism with the rotor (permanent magnet) of the motor 110. The d-axis is the axis along the direction of the magnetic flux formed by the rotor. and the q-axis is the axis along the direction of the torque generated by the motor 110 .
Other components of the q-axis target current setting section 121, the d-axis target current setting section 122, and the target current setting section 120 will be described in detail later.

The control unit 130 has a motor drive control unit 131 that controls the operation of the motor 110 and a motor drive unit 132 that drives the motor 110, as shown in FIG.
The control unit 130 also includes a motor current detection unit 133 that outputs a value corresponding to the actual current that actually flows through the motor 110, and converts the current detected by the motor current detection unit 133 into a current in the dq coordinate system. and a three-phase two-axis conversion unit 135 that
The control unit 130 also has a motor rotation angle calculation unit 136 that calculates a motor rotation angle θd, which is the actual rotation angle of the motor 110, based on the motor rotation angle signal θs from the rotation angle sensor 120 such as an encoder. ing.

A motor current detector 133 includes a U-phase current detector for detecting a U-phase current, which is a current that actually flows in the U-phase of the motor 110, which is a three-phase motor, and a U-phase current that actually flows in the V-phase of the motor 110. It has a V-phase current detection section for detecting a V-phase actual current, which is a current, and a W-phase current detection section for detecting a W-phase actual current, which is a current actually flowing in the W-phase of the motor 110. there is The U-phase current detector, the V-phase current detector, and the W-phase current detector detect the actual current flowing through each phase from the voltage generated across so-called shunt resistors connected to the U-phase, V-phase, and W-phase of the motor 110, respectively. Detect the value of

The 3-phase/2-axis conversion unit 135 receives the actual U-phase current, the actual V-phase current, and the W-phase actual current detected by the motor current detection unit 133, and the motor rotation angle calculated by the motor rotation angle calculation unit 136. θd is input. Then, the three-phase two-axis conversion unit 135 converts the U-phase actual current, the V-phase actual current, and the W-phase actual current into the d-axis actual current Ida, which is the value of the dq coordinate system, and the q-axis d-axis actual current Ida and q-axis actual current Iqa are output.
A motor rotation angle calculator 136 calculates a motor rotation angle θd based on a motor rotation angle signal θs from a rotation angle sensor 120 provided in the motor 110 .

The motor drive control unit 131 converts the d-axis actual current Ida calculated by the three-phase two-axis conversion unit 135 from the d-axis target current Idt set by the d-axis target current setting unit 122 of the target current setting unit 120. It has a d-axis subtraction unit 141d for subtraction. Further, the motor drive control unit 131 converts the q-axis target current Iqt calculated by the q-axis target current setting unit 121 of the target current setting unit 120 into the q-axis actual current calculated by the three-phase two-axis conversion unit 135. It has a q-axis subtractor 141q for subtracting Iqa.

The motor drive control unit 131 also has a current control amplifier 142d that outputs the d-axis target voltage Vdt so that the deviation (Idt-Ida) calculated by the d-axis subtraction unit 141d becomes zero. The motor drive control unit 131 also has a current control amplifier 142q that outputs the q-axis target voltage Vqt so that the deviation (Iqt-Iqa) calculated by the q-axis subtraction unit 141q becomes zero.

Further, the motor drive control unit 131 converts the d-axis target voltage Vdt and the q-axis target voltage Vqt output from the current control amplifier 142d and the current control amplifier 142q into U-phase target voltage Vut and V-phase target voltage Vut of the three-phase AC coordinate system. It has a 2-axis 3-phase converter 151 that converts the voltage Vvt to the W-phase target voltage Vwt.
The 2-axis 3-phase conversion unit 151 converts the d-axis target voltage Vdt and the q-axis target voltage Vqt to the U-phase target voltage based on a predetermined formula and the motor rotation angle θd calculated by the motor rotation angle calculation unit 136. The voltage Vut, the V-phase target voltage Vvt, and the W-phase target voltage Vwt are converted. That is, the 2-axis 3-phase converter 151 converts the applied voltage applied to the motor 110 based on the values output from the current control amplifiers 142d and 142q, in other words, feedback-controlled values and the motor rotation angle θd. decide.

Further, the motor drive control unit 131 provides a PWM control for PWM-driving the motor 110 based on the U-phase target voltage Vut, the V-phase target voltage Vvt, and the W-phase target voltage Vwt calculated by the two-axis three-phase conversion unit 151 . It has a PWM signal generator 160 that generates a (pulse width modulation) signal and outputs the generated PWM signal.

The motor drive unit 132 is a so-called inverter, and includes, for example, six independent transistors (FETs) as switching elements. , and the other three transistors are connected to the electrical coils of each phase and the negative (ground) line of the power supply. Then, the motor drive unit 132 controls the drive of the motor 110 by driving the gates of two transistors selected from the six transistors and switching these transistors.

(Details of target current setting unit 120)
As shown in FIG. 4, the target current setting unit 120 has a position subtraction unit 123 that subtracts the motor rotation angle θd calculated by the motor rotation angle calculation unit 136 from the position command pt. A position subtraction unit 123 calculates a deviation (pt-θd) by subtracting the motor rotation angle θd from the position command pt.
Here, the position command pt is output from a host controller (not shown). For example, the host control unit may be configured by a general-purpose personal computer or the like including a CPU, ROM, RAM, an operation unit such as a mouse and keyboard, and a display unit such as a liquid crystal display. For example, when the operator of the microscope 50 operates the operation unit to specify a position away from the enlarged image currently displayed on the display unit, the position command pt is information on the specified position. , the direction and distance from the center of the current observation field of view to the specified position are calculated and set.

The target current setting unit 120 also includes a motor rotation speed calculation unit 124 that calculates a motor rotation speed ωd, which is the rotation speed of the motor 110, based on the motor rotation angle θd calculated by the motor rotation angle calculation unit 136. there is The motor rotation speed calculator 124 calculates the motor rotation speed ωd by differentiating the motor rotation angle θd calculated by the motor rotation angle calculator 136 .

The q-axis target current setting unit 121 described above has a position control amplifier 125 that outputs the target rotation speed ωt so that the deviation (pt−θd) calculated by the position subtraction unit 123 becomes zero.
The q-axis target current setting unit 121 also includes a speed subtraction unit 126 that subtracts the motor rotation speed ωd calculated by the motor rotation speed calculation unit 124 from the target rotation speed ωt output from the position control amplifier 125. there is
The q-axis target current setting unit 121 also has a speed control amplifier 127 that outputs the q-axis target current Iqt so that the deviation (ωt−ωd) calculated by the speed subtraction unit 126 becomes zero.

The d-axis target current setting unit 122 described above has a position command speed calculation unit 128 that calculates a position command speed Vpt, which is the time rate of change of the position command pt. A position command speed calculator 128 calculates a position command speed Vpt by differentiating the position command pt.
Further, the d-axis target current setting unit 122 adjusts the d-axis target current Idt based on the position command speed Vpt calculated by the position command speed calculation unit 128 and the deviation (pt-θd) calculated by the position subtraction unit 123. It has a d-axis target current adjustment unit 129 for adjusting the current.

In the target current setting unit 120 configured as described above, the q-axis target current setting unit 121 causes the deviation (pt-θd) calculated by the position subtraction unit 123 to become zero and the position of the controlled object to reach the target position. When it reaches, the q-axis target current Iqt is set to zero. For example, if the x-direction position of the sample S is to be controlled, the q-axis target current Iqt of the x-motor 41 is set to zero when the x-direction position reaches the target position.

FIG. 6 is a diagram illustrating temporal changes in the d-axis target current Idt set by the d-axis target current setting unit 122. In FIG.
In the d-axis target current setting unit 122, the d-axis target current adjustment unit 129 adjusts the position command speed Vpt calculated by the position command speed calculation unit 128 when it is not zero or the deviation calculated by the position subtraction unit 123. If (pt-θd) is not zero, the d-axis target current Idt is set to zero. In other words, the d-axis target current adjusting section 129 sets the d-axis target current Idt to zero while the motor 110 is driving. In other words, the d-axis target current adjusting section 129 sets the d-axis target current Idt to zero when the q-axis target current Iqt is not zero.

On the other hand, when the position of the controlled object reaches the target position, in other words, when the position command speed Vpt calculated by the position command speed calculation unit 128 is zero and the position subtraction unit 123 When the calculated deviation (pt-θd) becomes zero, the d-axis target current Idt is set to a value other than zero. This is to set the d-axis target current Idt to a value other than zero in order to compensate for the amount of heat generated by the motor 110 that decreases due to the reduction of the q-axis target current Iqt. The d-axis is an axis along the direction of the magnetic flux formed by the rotor. The deviation of the position from the target position due to an increase in the current Idt is suppressed.

Then, the d-axis target current adjustment unit 129 sets the d-axis target current Idt so that it increases from zero to a predetermined current Idt0 at a predetermined increase rate. In other words, the d-axis target current adjustment unit 129 gradually increases the d-axis target current Idt to reach the predetermined current Idt0 after the predetermined increase time Ti has elapsed.

The predetermined current Idt0 and the predetermined increase time Ti can suppress temperature changes in parts that determine the position of the controlled object in order to prevent the position from deviating from the target position after the position of the controlled object reaches the target position. set to a valid value. For example, the x ball screw 35 and the x ball screw nut 36 can be exemplified as the parts that determine the position of the sample S in the x direction. A y ball screw 55 and a y ball screw nut 56 can be exemplified as parts that determine the position of the sample S in the y direction. A worm wheel 67a and a worm gear 67b can be exemplified as the parts that determine the position of the sample S in the rotational direction.

Heat generated when the motor 110 is driven is transferred to these parts, causing temperature changes in these parts. For example, taking the position of the sample S in the x direction as an example, the heat generated due to the supply of current to the x motor 41 changes the position of the sample S such as the x ball screw 35 and the x ball screw nut 36 in the x direction. , the position in the x-direction is determined as the target position with these parts thermally expanded. When the current supply to the x-motor 41 is stopped after the position in the x-direction reaches the target position, heat corresponding to the reduced current is no longer generated. The temperature of the part defining the position in the x-direction is reduced. When the temperature of these parts drops, they shrink, causing the position of the sample S to deviate from the target position, resulting in sample drift.

In view of the above matters, the predetermined current Idt0 and the predetermined increase time Ti are set in order to suppress the sample drift. For example, when the position of the sample S in the x direction is the target position and the q-axis target current Iqt is set to zero, the temperature of the parts that determine the position in the x direction, such as the x ball screw 35 and the x ball screw nut 36, and the predetermined The predetermined current Idt0 and the predetermined increase time Ti are set so that the temperatures of these parts become the same after the increase time Ti has elapsed. Therefore, the predetermined current Idt0 and the predetermined increase time Ti are determined according to the thermal conductivity of the part that determines the position of the sample S. For example, the predetermined increase time Ti is set to be longer as the thermal conductivity is smaller.

In the present embodiment, it can be exemplified that the predetermined current Idt0 and the predetermined increase time Ti are set in advance based on the measurement results and stored in the ROM. For example, the predetermined increase time Ti can be exemplified as one number of seconds determined from the range of 20 to 30 seconds. In this way, by slowly changing the d-axis target current Idt from zero to the predetermined current Idt0 over a predetermined increase time Ti, the position of the sample S is prevented from deviating from the target position.
Note that the predetermined current Idt0 and the predetermined increase time Ti may be set based on simulation results and calculation results.

Further, after the d-axis target current Idt reaches the predetermined current Idt0, in other words, after the predetermined increase time Ti elapses, the d-axis target current adjustment unit 129 adjusts the position command speed calculated by the position command speed calculation unit 128. The d-axis target current Idt is maintained at the predetermined current Idt0 while Vpt is zero and the deviation (pt-θd) calculated by the position subtraction unit 123 is zero.

Further, the d-axis target current adjustment unit 129 is adjusted when the position command speed Vpt calculated by the position command speed calculation unit 128 is not zero, or when the deviation (pt-θd) calculated by the position subtraction unit 123 is zero. , the d-axis target current Idt is decreased at a predetermined decrease rate. For example, when the d-axis target current Idt is the predetermined current Idt0, the position command speed Vpt calculated by the position command speed calculator 128 is not zero, or the deviation (pt −θd) is no longer zero, the d-axis target current adjustment unit 129 gradually reduces the d-axis target current Idt so that the d-axis target current Idt becomes zero after a predetermined decrease time Td has elapsed. Decrease. It is considered that the q-axis target current Iqt becomes a value other than zero when the position command speed Vpt becomes non-zero or when the deviation (pt-θd) calculated by the position subtraction unit 123 becomes non-zero. because it will be

Predetermined decrease time Td can be exemplified by being set in advance based on measurement results, simulation results, or calculation results, and stored in ROM. For example, the predetermined decrease time Td can be exemplified as one number of seconds determined from the range of 20 to 30 seconds. In this way, by slowly changing the d-axis target current Idt from the predetermined current Idt0 to zero over the predetermined decrease time Td, the position of the sample S is prevented from deviating from the target position.
In addition, it can be exemplified that the predetermined decrease time Td is the same as the predetermined increase time Ti. However, the predetermined decrease time Td may be different from the predetermined increase time Ti.

Further, the d-axis target current adjustment unit 129 is operated when the position command speed Vpt calculated by the position command speed calculation unit 128 is no longer zero while the d-axis target current Idt is being increased at the predetermined increase rate, or , the d-axis target current Idt is reduced to zero at the predetermined reduction rate when the deviation (pt-θd) calculated by the position subtraction unit 123 is no longer zero.

Further, when the d-axis target current adjustment unit 129 decreases the d-axis target current Idt, the position command speed Vpt calculated by the position command speed calculation unit 128 becomes zero, and the position command speed Vpt calculated by the position subtraction unit 123 becomes zero. When the calculated deviation (pt-θd) becomes zero, the d-axis target current Idt is increased at the predetermined increase rate.

As described above, the target current setting unit 120 sets the q-axis target current Iqt and the d-axis target current Idt, so that after the position of the sample S reaches the target position, the sample S may deviate from the target position due to temperature changes. is suppressed.

FIG. 7 is a flow chart showing the process of setting the d-axis target current Idt performed by the d-axis target current adjusting section 129. As shown in FIG. The d-axis target current adjustment unit 129 repeatedly executes this process at predetermined intervals (for example, one minute).
The d-axis target current adjustment unit 129 determines whether or not the d-axis target current Idt is zero (S701). When the d-axis target current Idt is zero (Yes in S701), the d-axis target current adjustment unit 129 determines whether or not the position command speed Vpt is zero (S702). If the position command speed Vpt is zero (Yes in S702), the d-axis target current adjustment unit 129 determines whether the deviation (pt-θd) calculated by the position subtraction unit 123 is zero ( S703). If the deviation (pt-θd) is zero (Yes in S703), the d-axis target current adjustment unit 129 increases the d-axis target current Idt to the predetermined current Idt0 at the above-described predetermined increase rate (S704).
If the position command speed Vpt is not zero (No in S702) and if the deviation (pt-θd) is not zero (No in S703), the d-axis target current adjusting section 129 terminates this process.

On the other hand, when the d-axis target current Idt is not zero (No in S701), the d-axis target current adjustment unit 129 determines whether or not the d-axis target current Idt is a predetermined current Idt0 (S705). When the d-axis target current Idt is the predetermined current Idt0 (Yes in S705), the d-axis target current adjustment unit 129 determines whether or not the position command speed Vpt is zero (S706). If the position command speed Vpt is zero (Yes in S706), the d-axis target current adjustment unit 129 determines whether the deviation (pt-θd) calculated by the position subtraction unit 123 is zero ( S707). If the deviation (pt−θd) is zero (Yes in S707), the d-axis target current adjustment unit 129 ends this process to maintain the d-axis target current Idt at the predetermined current Idt0.

If the position command speed Vpt is not zero (No in S706), the d-axis target current adjustment unit 129 decreases the d-axis target current Idt from the predetermined current Idt0 to zero at the above-described predetermined decrease rate (S708). If the deviation (pt−θd) is not zero (No in S707), the d-axis target current adjustment unit 129 decreases the d-axis target current Idt from the predetermined current Idt0 to zero at the above-described predetermined decrease rate ( S708).

On the other hand, if the d-axis target current Idt is not equal to the predetermined current Idt0 (No in S705), the d-axis target current adjustment unit 129 determines whether or not the d-axis target current Idt is being increased (S709). ). In other words, this process determines whether or not the d-axis target current adjustment unit 129 has reached the predetermined current Idt0 after the d-axis target current adjustment unit 129 starts increasing the d-axis target current Idt to the predetermined current Idt0 at a predetermined rate of increase in S704. It determines whether In the processing of S709, the d-axis target current adjustment unit 129 may determine whether or not the predetermined increase time Ti has elapsed after starting to increase the current to the predetermined current Idt0 at the predetermined increase rate in S704.

If the d-axis target current Idt is being increased (Yes in S709), the d-axis target current adjustment unit 129 determines whether or not the position command speed Vpt is zero (S710). When the position command speed Vpt is zero (Yes in S710), the d-axis target current adjustment unit 129 determines whether the deviation (pt-θd) calculated by the position subtraction unit 123 is zero ( S711). If the deviation (pt−θd) is zero (Yes in S711), the d-axis target current adjustment unit 129 terminates this process so as to keep the d-axis target current Idt increasing.

On the other hand, if the position command speed Vpt is not zero (No in S710), the d-axis target current adjustment unit 129 reduces the d-axis target current Idt to zero at the above-described predetermined reduction rate (S708). Also, if the deviation (pt-θd) is not zero (No in S711), the d-axis target current adjustment unit 129 reduces the d-axis target current Idt to zero at the above-described predetermined reduction rate (S708).

On the other hand, if the d-axis target current Idt is not being increased (No in S709), the d-axis target current Since Idt has not reached zero, the d-axis target current adjustment unit 129 determines whether or not the position command speed Vpt is zero (S712). If the position command speed Vpt is zero (Yes in S712), the d-axis target current adjustment unit 129 determines whether the deviation (pt-θd) calculated by the position subtraction unit 123 is zero ( S713). If the deviation (pt-θd) is zero (Yes in S713), the d-axis target current adjustment unit 129 increases the d-axis target current Idt to the predetermined current Idt0 at the above-described predetermined increase rate (S704).
On the other hand, if the position command speed Vpt is not zero (No in S712) and if the deviation (pt−θd) is not zero (No in S713), the d-axis target current adjustment unit 129 adjusts the d-axis target current Idt This process is terminated in order to maintain the decrease of .

The d-axis target current adjustment unit 129 performs this setting process, whereby the d-axis target current Idt is set to an appropriate value with high accuracy.
As a result, the temperature change of the parts that determine the position of the controlled object that is moved by driving the motor 110 is suppressed. It is possible to position the table on which S is placed with high accuracy.

In the above-described embodiment, the d-axis target current adjustment unit 129 is controlled when the position command speed Vpt calculated by the position command speed calculation unit 128 is not zero, or when the position command speed Vpt calculated by the position subtraction unit 123 is When (pt-θd) is not zero, the d-axis target current Idt is set to zero, but is not particularly limited to zero. If the position command speed Vpt calculated by the position command speed calculation unit 128 is not zero, or if the deviation (pt-θd) calculated by the position subtraction unit 123 is not zero, the d-axis target current adjustment unit 129 may be set to any negative value instead of zero. Then, when the position command speed Vpt is zero and the deviation (pt-θd) is zero, the d-axis target current adjustment unit 129 adjusts the d-axis target current Idt from this arbitrary negative value to It is preferable to increase the current up to a predetermined current Idt0 at a predetermined rate of increase. Further, when the d-axis target current adjustment unit 129 sets the d-axis target current Idt to the predetermined current Idt0, the position command speed Vpt becomes non-zero or the deviation (pt-θd) becomes non-zero. In this case, it is preferable to decrease the d-axis target current Idt from the predetermined current Idt0 to this arbitrary negative value.

In the above-described embodiment, an example in which the control device 100 is used to control the driving of the motor 110 of the microscope 50 is shown, but the motor 110 of the microscope 50 is not particularly limited. In other words, the object to be positioned is not limited to the sample S observed by the microscope 50, and the table on which the sample S is placed, such as the x-table 33, y-table 43, and rotation table 66. The control device 100 may be applied to all three-phase motors that are driven to move an object to be positioned.

In the above-described embodiment, the motor current detection section 133 is exemplified by using three current detection sections, namely, the U-phase current detection section, the V-phase current detection section, and the W-phase current detection section. Not limited to configuration. Since the sum of the current values of the U-phase real current, the V-phase real current, and the W-phase real current is zero, the current values of the remaining phases can be calculated by detecting the current values of the two phases. Therefore, a configuration in which any one of the U-phase current detector, the V-phase current detector, and the W-phase current detector is omitted may be applied.

33...x table, 41...x motor, 43...y table, 61...y motor, 50...scanning electron microscope, 66...rotation table, 73...r motor, 100...control device, 120...target current setting section, 121 ... q-axis target current setting section, 122 ... d-axis target current setting section, 130 ... control section

Claims (8)

A control device for a three-phase motor driven to move a table in an electron microscope ,
a target current setting means for setting a d-axis target current and a q-axis target current in a dq coordinate system as target currents to be supplied to the motor;
The target current setting means is a control device that increases the d-axis target current when decreasing the q-axis target current. 2. The control device according to claim 1, wherein said target current setting means increases said d-axis target current to a predetermined current when said q-axis target current is changed from a non-zero value to zero. 3. The target current setting means according to claim 2, wherein said target current setting means gradually increases said d-axis target current so as to reach said predetermined current after a predetermined increase time has passed since said q-axis target current is set to zero. Control device. 4. The target current setting means according to any one of claims 1 to 3, wherein when the position command speed is zero and the positional deviation is zero, the q-axis target current is set to zero and the d-axis target current is increased from zero. 2. The control device according to item 1. A control device for a three-phase motor driven to move a table in an electron microscope ,
a target current setting means for setting a d-axis target current and a q-axis target current in a dq coordinate system as target currents to be supplied to the motor;
The target current setting means is a control device for decreasing the d-axis target current when increasing the q-axis target current. 6. The control device according to claim 5, wherein said target current setting means reduces said d-axis target current to zero when said q-axis target current is changed from zero to a value other than zero. 7. The target current setting means according to claim 6, wherein the target current setting means gradually decreases the d-axis target current so that the q-axis target current becomes zero after a lapse of a predetermined decrease time from when the q-axis target current is set to a value other than zero. controller. 8. The target current setting means according to any one of claims 5 to 7, wherein the q-axis target current is set to a non-zero value and the d-axis target current is reduced when the position command speed or the positional deviation is no longer zero. 1. The control device according to claim 1.

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